APPLICANT'S DESCRIPTION: (Provided by Applicant) The In vivo PDT: Animals, Dosimetry, and Statistics Core will provide equipment, services and training necessary for a wide range of PDT experiments on living animals. The Core aims to catalyze the fusion of biological and physics expertise and together with appropriate dosimetry and statistical input allow animal experiments to be carried out as efficiently and economically as possible. The Core has three broad Specific Aims: (1) Experimental animals. (a) The core will provide equipment and support for the ordering, identification by implanted radio-frequency tags, tracking and record keeping of animals. (b) Provide equipment, anesthetics and assistance in the treatment and post-operative monitoring of animals, this will include digital electronic calipers for measurements of tumor dimensions. Conduct pilot studies to determine times after injection for intravascular and extravascular localizations of BPD, test for phototoxicology during PDT with the photosensitizers BPD and ALA-induced PPIX, and test implanted light-dose measurement fibers, correlate fiber-measured fluorescence with extracted photosensitizer content, and test oxygen measuring apparatus in small rodent tumor models. (d) Provide education and training for investigators, concerning MGH SRAC and federal forms and regulations on animal experiments, provide manuals dealing with anesthesia, surgical techniques and proper animal husbandry of small rodents during experiments and ensure that the Program remains in compliance with Institutional and USDA guidelines. A full-time technician will be available for the performance of these duties. (2) Light delivery and dosimetry. The core will provide evaluation, acquisition, implementation of technology, and training in its use in the areas of (a) Light delivery including KTP-pumped dye laser and diode lasers, LED devices, fiber optics and wavelength and power measurement devices. (b) In vivo light dosimetry based on a system using implanted fiber optics that provide on-line measurements of the dose-rate and total accumulated light dose at each monitor point. In vivo photosensitizer quantitation based on a system using either surface or implanted fiber optics that can measure fluorescence from tissue quantitatively, and independent of the tissue's intrinsic optical properties, (d) Measurements of bulk tissue oxygen pressure and blood flow using a fiber optic based system with a fluorescent tipped probe together with a Doppler blood flow probe. A full-time technician will be available for the performance of these duties. (3)Statistics (a) Provide statistical advice in planning experimental protocols in order to achieve the desired aims in a manner that is cost-effective, humane, and scientifically sound. (b) Provide advice and assistance in data collection and data management. (c) Provide advice and assistance in statistical analysis of data and interpretation of results.